What do you think is the moral of the ballad "The Demon Lover?"

The moral of the story—it's not actually a ballad—is that one can't escape from the past, no matter how hard one tries. That's the dire predicament that Kathleen, the story's protagonist, finds herself in. She had hoped to have moved on from her past life, to leave behind the love that had once existed between herself and a soldier killed in World War I. But she can't.
Clearly, that love was a very strong one; so strong in fact that it has risen, Dracula-like from the dead, after all these years to manifest itself in the creepiest and most uncomfortable way imaginable. Love never dies, as they say, and it certainly doesn't here, even though—Lord knows—Kathleen would dearly wish it were otherwise. Try as she might she cannot escape from her past, which with its intense passion and unfulfilled promise, holds her in the palm of its wizened claw in a vice-like grip.

It can be argued that the moral of the story is that war results in devastating consequences for humanity. The story demonstrates that war perpetrates suffering on both soldiers and civilians alike. The costs of war are thus physical, spiritual, economic, and social in nature. However, who can fully and adequately quantify the devastating effects of war?
In the story, Mrs. Drover's soldier lover returns to fulfill a twenty-five year old promise to her. However, the author does not reveal whom Mrs. Drover sees in the taxi. Instead, the author leaves us to decide how we will interpret Mrs. Drover's frantic screams. Many have argued that Mrs. Drover's "demon lover" is the actual taxi driver. However, others maintain that war has so traumatized Mrs. Drover that she has lost her grip on reality.
Today, many mental health experts contend that war has a devastating effect on women. More women are affected by mental disorders in the face of war than men. In Afghanistan (a war-torn country), a study documents that almost 70% of respondents showed symptoms of depression. Meanwhile, a similar percentage experienced daily feelings of acute anxiety. Women had higher rates of anxiety and depression than men in both cases. So, psychological and emotional scarring are definitely induced by horrific war experiences.